Grant Archive

Electric utilities and regulators are constantly evaluating means to improve both reliability and public safety while also reducing cost. As trees are among the most frequent causes of interruptions and represent one of the largest maintenance costs, vegetation management is a frequent subject of inquiry.

Recent development in tree risk management has moved the arboriculture industry from simply identifying hazard trees, toward a Tree Risk Assessment process where both the risk and consequences of a tree failure are taken into account. The primary inputs include the likelihood of failure, likelihood of impact and consequence of the potential impact to derive a risk rating that ranges from low to extreme. While determining the likelihood of impact and the potential consequence has a degree of subjectivity, these two inputs are reasonably objective. Yet, determining the likelihood of failure continues to be a challenging task as there are a large host of factors that potentially influence the tree stability. Which explains why understanding the probability of tree failure is listed as one of the Utility Arborist Association’s top five research priorities.

Trees continue to be among the leading causes of electric distribution system service interruptions. Tree maintenance is often the largest O&M expenses. Utilities are increasingly looking beyond routine maintenance zones to address tree conditions that may lead to interruptions. Failure can be categorized as either from roots, stems or branches. Our team will review what is known about failures from these three zones, concentrating on why seemingly healthy trees fail. The approach of investigating why seemingly healthy trees fail is important as it has been reported that as many as 50-65% of failures take place in trees with no externally detectable defects. This suggests the utility arboriculture industry has much to learn as to why trees fail and how to predict the likelihood of failure.

Development of failure risk probability models to include observable and non-observable defects and lack thereof within severity ranges will help utilities and regulators better understand the risks and benefits of programs designed to further reduce tree-caused outages over specific time periods. Environmental and fiscal responsibility can be enhanced through prioritization of high failure probability conditions.

The project will result in a technical report that explores key issues, summarizes the literature review and provides a basis for future investigations.

On the basis of the literature review and associated work outlined in work scope, a technical report will be developed. A summary of findings will be prepared for publication in the UAA Utility Arborist Newsline and Arboriculture & Urban Forestry journal.

The results of this project will lay the groundwork for a future project by identifying the methodology, protocols, and criteria for designing that future study to collect tree failure data and develop failure models. The models may be used by utility vegetation managers to:

Identify high risk trees that may lead to tree-caused outages, thereby reducing total tree outages.

In cities, paved roads and buildings prevent the course that rainfall would naturally take, infiltrating into soil and replenishing groundwater. Instead, rainfall becomes “urban runoff,” causing beach closures, stream erosion, algal blooms and impaired water quality in urban streams. Water sensitive urban design (WSUD) systems capture and treat urban runoff that would otherwise impact ecosystem and human health. Stormwater biofilters are one type of WSUD that rapidly infiltrate runoff to the underlying water table. Biofilters rely on healthy vegetation to properly function. Due to the rapid infiltration of runoff, plants in these systems can be more susceptible to drought and often die during extended dry periods. Trees are particularly susceptible during the establishment phase before roots have grown deep enough access the water table. A type of fungus, mycorrhizae, forms a symbiotic relationship with plants in biofilters and can improve the ability of plants to reach otherwise inaccessible water in the soil.

Our study will evaluate the ability of mycorrhizae to improve plant health in stormwater biofilters during extended dry periods. Among a few herbaceous species, we will inoculate two tree species with mycorrhizae: Melalueca ericofolia (swamp paperbark) and Leptospermum continentale (prickly tea-tree), which are native Australian tree species and common in Melbourne biofilters. We will then evaluate the growth of these plants and growth of non-inoculated plants by measuring the photosynthesis on a regular basis. Based on this test, we will select the most appropriate species for a follow evaluation on the effect of mycorrhizae on improving the ability of immature trees to survive and improve water quality following extended dry periods. We expect that our results will help inform management of trees in biofilters during the establishment phase in areas prone to drought or seasonal dry periods, particularly in Australian cities.

Urban forests have both positive and adverse effects on human well-being, while their sustainability, given climate change and invasive species, is at risk. Setting targets for key attributes such as optimal tree density, age/size distribution, species variety, in this context will thus require precise data on public and private trees. Tree detection performed using airborne LIDAR 3D models can provide information on the size of most urban trees, and can also identify species or species groups with a good accuracy. We propose to test these methods on existing LIDAR data for the City of Montreal, used as a case study representative of North American cities, and derive the above-mentioned key attributes. From these we will produce indicators at the neighborhood level for the entire island of Montreal (500 km2) such as: local density and height of trees, species biodiversity, etc. The overarching goal is to develop methods for characterizing a) individual trees and b) features of the urban forest at the neighborhood level.

This project will be carried out in close collaboration with the City of Montreal, Canada. Having started to work on the above goals with them in 2018, but without external funding, the foundations of the proposed project are already laid out. Because the software tools will have be delivered and explained to the personnel of the City of Montreal at the end of the project, the City’s personnel will be autonomous for applying the methods as soon as 2019, as well as in the future, such that updating the data outputs will be possible. These outputs, i.e. a map of all individual trees visible from the air (both public and private) and their attributes and species, as well as maps of neighborhood level indicators, will help guide the City of Montreal in decisions for creating an urban forest that has a positive impact of human health and well-being, and that is more resilient to climate change and invasive insect species. The results will be disseminated at three levels: at the City of Montreal itself (one-day workshop), at the regional level (during a presentation at a conference attended by municipal actors from the entire province of Quebec, Canada), and internationally (during a presentation at one conference in the U.S.A., and in a paper in one international journal). Based on Montreal’s case, we hope that the adoption the proposed approach and related technology by other municipalities will be facilitated.

Imagine a tree that protects stream banks, shelters farms from wind and blowing snow, grows rapidly, thrives in urban settings, lives for over 100 years, tolerates cold, heat and salt, has few diseases or insect pests, and displays a beautifully shaped canopy with small seeds and handsome foliage. These are the ash trees native to America, primarily green ash and white ash and they are disappearing because of emerald ash borer (EAB), an insect accidentally imported from Asia. EAB is spreading rapidly across the United States, killing 98-100% of the ash trees it infests throughout forests, along rivers, in rural regions and in urban communities. Dead tree removal and insecticide treatments cost rural and urban communities over 1.7 billion dollars in 2011 alone and the cost continues to increase.

The good news is that a few green and white ash trees (<1%) survive for years after all other local ash trees have died. Scientists working for United States Forest Service and the University of Notre Dame have confirmed that most of these survivors have the ability to fight EAB attack and different trees use different defensive strategies. This grant from TREE Fund will enable this team of scientists to identify groups of chemical compounds that fight off EAB in individual trees and the genes that produce these compounds. This work will identify the best group of offspring from parent trees having the highest defensive responses.

Increasing the rate at which naturally-occurring defensive traits in ash are identified decreases the time it takes to produce trees with enough resistance to survive in the wild. Within a few generations, the seed from these trees can be distributed throughout the Midwest to establish local seed orchards for restoration. This will reduce EAB from a deadly plague to a minor pest. The project relies on a team approach and wise use of multiple techniques including forest monitoring, tree propagation, applied entomology, a small dose of high tech analytical wizardry, tried and tested plant breeding techniques and a lot of hard work. The impact will be the return of American ash trees to the landscapes where they once grew, shading our rivers, beautifying our neighborhoods and lifting our hearts with the sight of their beautiful green foliage.